1. Field of the Invention
The present invention relates to white defect repairing method and apparatus of a photomask which repair a white defect generated in a manufacture process of a semiconductor photomask, a manufacturing method of a photomask, and a manufacturing method of a semiconductor device.
2. Description of the Background Art
Heretofore, repair of a white defect of a mask film on a quartz substrate in a photomask for use in manufacture of a semiconductor integrated circuit has been performed by depositing a carbon film on a white defect portion in a focused ion beam repair apparatus (hereinafter referred to as “FIB apparatus”) or the like.
In general, one factor to determine a performance of the repair apparatus of the photomask is an alignment precision during the repair, that is, a repair precision. The repair precision improves with improvement of the apparatus, but on the other hand, miniaturization and precision of devices also advance. Therefore, in all generations, the sufficient precision has not been achieved. That is, a necessary level of the repair precision has not been achieved yet in a period where such a necessary level is required.
Pass or fail of a repaired trace is usually judged by inspection with an image quality evaluation apparatus having the same wavelength and the same optical system as in an exposure apparatus. A typical example of the evaluation apparatus is an aerial measurement system (AIMS) made by Carl Zeiss, Inc, and this system is capable of making all the same illumination conditions as in the case of the manufacture of the devices. In the pass or fail judgment, a wafer image is taken by use of this AIMS to measure a critical dimension (CD) and an image intensity. In many cases, criterion of the pass is within a fluctuation range of several percent to 10 percent.
When this pass criterion of the AIMS is not satisfied after the white defect is repaired with the FIB apparatus, the FIB repair must be performed again, but in this case, an edge of the carbon film is not easily seen in the image of the FIB apparatus, which makes the additional repair difficult. Therefore, in a case where a position of the film deviates, it is required that the already deposited carbon film is once peeled and the deposition is then performed again. This remarkably decreases a throughput of a repair process. The FIB apparatus has a problem of a damage in taking the image. In a mask for exposure having an exposure wavelength of 193 nm, the number of re-repairs is limited to two or three.
As an another drawback of the white defect repair by the deposition of the carbon film, there is also a problem that an edge skirt of the film referred to as a halo adversely affects an image quality during wafer transfer. In particular, this problem is remarkable in the FIB apparatus having a large beam diameter. In addition, it is impossible to attach the micro carbon film having a diameter equal to or less than the beam diameter.
For such a reason, there are also investigated repair methods in which the FIB apparatus is used but any carbon film is not deposited. They correspond to methods described in Jpn. Pat. Appln. KOKAI Publication No. 2003-121991 titled “White Defect Repair Method of Photomask” and the like. However, in these methods, the influence of the halo on the image quality decreases, but a conventional problem remains unsolved in that the re-repair must be performed in a case where the pass criterion is not satisfied after the repair. That is, it is impossible to judge a portion of the image to be next repaired by the FIB apparatus during the re-repair. Moreover, the repair precision itself does not exceed a range of a basic precision of the FIB apparatus.